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Thalattosuchia is a
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...
of marine
crocodylomorph Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. During Mesozoic and early Cenozoic times, cro ...
s from the
Early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...
to the
Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145& ...
that had a
cosmopolitan distribution In biogeography, cosmopolitan distribution is the term for the range of a taxon that extends across all or most of the world in appropriate habitats. Such a taxon, usually a species, is said to exhibit cosmopolitanism or cosmopolitism. The extr ...
. They are colloquially referred to as marine crocodiles or sea crocodiles, though they are not members of
Crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest livi ...
and records from Thailand and China suggest that some members lived in freshwater. The clade contains two major subgroupings, the
Teleosauroidea Teleosauroidea is an extinct superfamily of thalattosuchian crocodyliforms living from the Early Jurassic to the Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostr ...
and
Metriorhynchoidea Metriorhynchoidea is an extinct superfamily of thalattosuchian crocodyliforms from the Early Jurassic to the Early Cretaceous (Toarcian - Valanginian, possibly as late as early Aptian) of Europe, North America and South America. Metriorhynchids a ...
. Teleosauroids are not greatly specialised for oceanic life, with back osteoderms similar to other crocodyliformes. Within Metriorhynchoidea, the
Metriorhynchidae Metriorhynchidae is an extinct family (biology), family of specialized, aquatic metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period (Bajocian to early Aptian) of Europe, North America and South America. The name ...
displayed extreme adaptions for life in the open ocean, including the transformation of limbs into flippers, the development of a tail fluke, and smooth, scaleless skin.


Discovery and naming

The term Thalattosuchia was coined by Fraas in 1901.Fraas E. 1901. Die Meerkrokodile (Thalattosuchia n. g.) eine neue Sauriergruppe der Juraformation. ''Jahreshefte des Vereins für vaterländische Naturkunde, Württemberg'' 57: 409-418. Various authors considered Thalattosuchia an infraorder or a suborder within " Mesosuchia". However, the term "Mesosuchia" is a
paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In ...
group, and as such is no longer used. For consistency, the Thalattosuchia are here placed at suborder rank, although the order that contains it is unnamed. The exact phylogenetic position of Thalattosuchia is uncertain, with them either being interpreted as members of
Neosuchia Neosuchia is a clade within Mesoeucrocodylia that includes all modern extant crocodilians and their closest fossil relatives. It is defined as the most inclusive clade containing all crocodylomorphs more closely related to ''Crocodylus niloticu ...
or basal members of Crocodylomorpha, with the similarities to neosuchians possibly being due to
convergence Convergence may refer to: Arts and media Literature *''Convergence'' (book series), edited by Ruth Nanda Anshen *Convergence (comics), "Convergence" (comics), two separate story lines published by DC Comics: **A four-part crossover storyline that ...
. Since Buffetaut (1982) demonstrated the shared characteristics of the early forms of
Metriorhynchidae Metriorhynchidae is an extinct family (biology), family of specialized, aquatic metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period (Bajocian to early Aptian) of Europe, North America and South America. The name ...
and
Teleosauridae Teleosauridae is a family of extinct typically marine crocodylomorphs similar to the modern gharial that lived during the Jurassic period. Teleosaurids were thalattosuchians closely related to the fully aquatic metriorhynchoids, but were less ad ...
, Thalattosuchia has consisted of these two families.Buffetaut, E. 1982. Radiation évolutive, paléoécologie et biogéographie des Crocodiliens mésosuchienes. ''Mémoires Societé Geologique de France'' 142: 1–88. The oldest records of thalattosuchians date to the
Sinemurian In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and ...
and
Pliensbachian The Pliensbachian is an age (geology), age of the geologic timescale and stage (stratigraphy), stage in the stratigraphic column. It is part of the Early Jurassic, Early or Lower Jurassic epoch (geology), Epoch or series (stratigraphy), Series an ...
stages, represented by indeterminate remains from Argentina, Chile, and India. The latest records date to the
Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145& ...
. Some of the early members of Teleosauridae have been discovered in non-marine deposits. The systematics of the genus ''
Pelagosaurus ''Pelagosaurus'' (meaning "lizard of the open sea") is an extinct genus of thalattosuchian crocodyliform that lived during the Toarcian stage of the Lower Jurassic, around 183 Ma to 176 Ma (million years ago), in shallow epicontinental seas that ...
'' are confused, with differencing topologies placing it as either a teleosaurid,Gasparini Z, Pol D, Spalletti LA. 2006. An unusual marine crocodyliform from the Jurassic-Cretaceous boundary of Patagonia. ''Science'' 311: 70-73. or as the sister taxon to a Teleosauridae + Metriorhynchoidea clade. Others considered ''Pelagosaurus'' to be a basal metriorhynchoid.


See also

*
List of thalattosuchian-bearing stratigraphic units List of thalattosuchian-bearing stratigraphic units, or geologic formations. Introduction Thalattosuchia is the name given to a clade of marine crocodylomorphs from the Early, Middle, and Late Jurassic period eras to the Early Cretaceous pe ...
*
List of marine reptiles Following is a list of marine reptiles, reptiles which are adapted to life in marine or brackish environments. Extant The following marine reptiles are species which are currently extant or recently extinct. Crocodiles :*''Crocodylus'' ::'' Cr ...


References


Further reading

*Fraas, E. (1902). "Die Meer-Krocodilier (Thalattosuchia) des oberen Jura unter specieller Berücksichtigung von ''Dacosaurus'' und ''Geosaurus''". ''Paleontographica'' 49: 1-72.


External links


"Ancient ocean-going crocodiles mimicked whales and dolphins"
at The Guardian, 20 Apr 2020 {{Taxonbar, from=Q2300406 Prehistoric animal suborders Tetrapod suborders Prehistoric marine crocodylomorphs Jurassic crocodylomorphs Early Cretaceous crocodylomorphs Sinemurian first appearances Early Cretaceous extinctions